(1) Field of the Invention
The present invention relates to an optical cross connect apparatus or system and an optical network, to which the WDM (Wavelength Division Multiplex) transmission technique is applicable.
(2) Description of the Related Art
So far, optical communications have principally employed point-to-point TDM (Time Division Multiplex) transmission. However, with the spread of the Internet or the like, the communication traffic volume (information communication volume) is on the explosive increase and an expectation or possibility exists that the information communication volume further increases afterwards; therefore, two approaches, that is, the speed-up of the TDM transmission and the high-density multiplexing in the WDM transmission, have taken place in the recent years.
Of these, the WDM transmission is expected as a technique to increase the communication volume without gaining the signal rate by utilizing the optical broadband characteristics effectively. The WDM transmission has been introduced initially for the purpose of increasing the number of wavelengths to be multiplexed in the field of the existing point-to-point transmission. Additionally, the configuration of a high-flexibility high-reliability optical network (such as a ring network) has started through the employment of the optical ADM (Add Drop Multiplexer) capable of dropping/adding optical signals in units of wavelengths.
In such a technical background, for example, an optical cross connect system (OCCS), designated generally at reference numeral 100 in FIG. 63, is expected as a next-generation system capable of constructing a higher-flexibility higher-reliability optical network.
In FIG. 63, the OCCS 100, in contrast with the existing systems, can accommodate a large number of input/output optical fibers and, additionally, can accept optical signals different in transmission rate from each other, such as an OC (Optical Carrier)-192 (STM (Signal Transfer Module)-64 ≈(almost equal) 10 Gb/s) and an OC-48 (STM-16≈2.5 Gb/s) and an OC-12 (STM-4≈620 Mb/s), through proper optical interfaces 300 to 600 so that the setting [exchange (cross connect)] of optical paths in units of wavelengths is feasible in a manner that an optical routing section (cross connect section) 200 conducts switching (routing) among output paths or performs wavelength conversion for or on these optical signals in units of wavelengths.
Accordingly, for example, if, as shown in FIG. 63, the OCCS 100 accommodates optical fibers constituting a trunk line system for a ring network or the like to form optical links (Inter-Office Link) 700A and 700B and additionally accommodates optical fibers organizing a different network to establish an optical link (Intra-Office Link) with the different network, it becomes possible to add an optical signal from the different network to the trunk line system in units of wavelengths or to drop a portion of an optical signal running on the aforesaid trunk line system to the different network.
In consequence, the OCCS 100 is capable of setting up a connection between the existing ring networks put individually in operation or of making a connection of the existing network other than ring networks to a ring network, thus constructing a new large-capacity optical network. For this reason, as a system which plays most important role in a future optical network, much attention has been focused on this OCCS 100.
A detailed description will be given hereinbelow of the aforesaid routing section 200 constituting an essential part of the OCCS 100. FIG. 64 is a block diagram showing one example of principle configuration of the optical routing section 200. In FIG. 64, the optical routing section 200 employs a typical non-blocking type switch circuit (three-stage switch configuration), referred to as a cross (Clos) type.
Furthermore, as FIG. 64 shows, the first-stage switch unit 200A comprises k n-input 2n-output (nxc3x972n) type switch circuits 201, the second-stage (intermediate-stage) switch unit 200B comprises 2n k-input k-output (kxc3x97k) type switch circuits 202, and the third-stage switch unit 200C comprises k 2n-input n-output (2nxc3x97n) type switch circuits 203.
Incidentally, the xe2x80x9cMxc3x97M switch circuitxe2x80x9d taken here signifies a switch which exhibits an ability to switch (selectively establish an output path) any one of M inputs (M denotes an integer being two or more) to any one of the M outputs. Furthermore, the aforesaid k corresponds to the number of input ports (output ports), for example, one optical fiber is connected (accommodated) to one port. Still furthermore, the aforesaid n is equivalent to the number of wavelengths multiplexed (the number of input wavelength types), for example, if an optical signal to be transmitted through the one optical fiber forms a 16-wavelength multiplexed optical signal, n=16, and if it forms a 32-wavelength multiplexed optical signal, n=32. That is, the number N of input/output channels of the optical routing section 200 shown in FIG. 64 becomes N=nxc3x97k.
FIG. 65 shows a detailed configurational example of the optical routing section 200 based upon the foregoing three-stage cross type switch circuit arrangement. This configuration shown in FIG. 65 is such that the number of input ports (output ports) is set at k=8 and the number of wavelengths to be multiplexed per port assumes n=32 (xcex1 to xcex32), that is, the total number of input/output channels assumes N=8xc3x9732=256, while the first-stage switch unit 200A employs 16 16xc3x9732 switch circuits 201, the second-stage switch unit 200B uses 32 16xc3x9716 switch circuits 202 and the third-stage switch unit 200C uses 16 32xc3x9716 switch circuits 203.
In addition, each of the 16=32 switch circuits 201 of the first-stage switch unit 200A and each of the 32xc3x9716 switch circuits 203 of the third-stage switch unit 200C are constructed using two 16xc3x9716 switch circuits 211 and 16 1xc3x972 switch circuits 210. That is, in the configuration shown in FIG. 65, the basic size of the switch circuits (basic switch size) becomes 16xc3x9716.
Furthermore, in FIG. 65, reference numeral 204 depicts each of 8 optical demultiplexer (filters) provided with each of the input ports. Each of these optical demultiplexers 204 demultiplexes a wavelength multiplexed optical signal from the corresponding input port according to each of wavelengths xcex1 to xcex32 so that, for example, the optical signals respectively having wavelengths of xcex1 to xcex16 are inputted to the 16xc3x9732 switch circuits 201 in odd numbers while the remaining optical signals respectively having wavelengths of xcex17 to xcex32 are inputted to the even-numbered 16=32 switch circuits 201.
Still furthermore, reference numeral 205 denotes each of wavelength converters, whose number equals the total number of input/output channels (namely, 256), for converting a wavelength xcexx (where x=1 to 32) of an optional input optical signal after subjected to the switching (routing) by the switch units 201 to 203 into a predetermined wavelength to an output port, and the wavelength converters 205 allow the optical routing section 200 to output an optical signal with an optional wavelength to an optical input port as an optical signal with a desired wavelength (idle channel) at a desired output port.
Moreover, reference numeral 206 designates each of 8 optical multiplexers provided with each of the output ports, and each of the optical multiplexers 206 multiplexes (wavelength-multiplexes) the optical signals, respectively converted in wavelength in the wavelength converters 205, at every output wavelengths (xcex1 to xcex32) to each of the output ports, and outputs the multiplexed optical signal to the corresponding output port.
Still moreover, reference numeral 207 (208) represents each of optical amplifiers, whose number is 8xc3x972=16, provided with each of the input ports (each of the output ports), and the optical amplifiers 207 (208) are appropriately used for compensating for an optical loss or the like occurring due to the routing of the optical signals in the switch units 200A to 200C (switch circuits 201 and 202) (the installation of the optical amplifiers 207 (208) is not required particularly if the loss is disregardable).
With the above-described configuration, the foregoing optical routing section 200 can output an optical signal with an arbitrary wavelength to an arbitrary input port as an optical signal with a desired wavelength to a desired output port [that is, it is capable of accomplishing the path setting (cross connect) in units of wavelengths]. For example, in a case in which an optical signal with an input wavelength of xcex1 to the uppermost output port (1) is outputted as an optical signal with an output wavelength of xcex32 to the lowermost output port (8), the optical signal with the input wavelength of xcex1 to the output port (1) is inputted to the lowermost wavelength converter 205. Accordingly, the switching setting for the switch units 200A to 200C (switch circuits 201 and 202) is made to achieve this input of the optical signal.
As described above, the OCCS 100 provides a large-scale optical switching system different from the existing systems.
Meanwhile, the WDM transmission technique handling a level up to 32-wavelength multiplexing has already been available, and the techniques handling higher levels, such as 64-wavelength multiplexing and 128-wavelength multiplexing are currently at the trial and study stage. For this reason, the aforesaid OCCS 100 needs to accept all of these signals, and reaches a large system scale naturally.
Hence, the following two points exist chiefly as important objects arising with the OCCS 100. That is, one point is the size reduction of the system which tends to have a larger scale and the other is to offer an OCCS 100 with a proper system size matching with the needed value of information. The latter can namely be handled as an object in the extensibility of the system. In general, for the WDM transmission technique, an increase in the number of wavelengths to be multiplexed is made to cope with an increase in volume of information, which leads naturally to an increase in the system size of the OCCS 100, while it is desirable that this system size is proportional to the increase/decrease in the number of wavelengths.
That is, in addition to tackling the size reduction and economization of the system, the excellent extensibility coping with the increase in the number of wavelengths to be accepted or accommodated constitutes an important point on the development of the OCCS 100 (especially, the optical routing section 200). Additionally, conceivably, for the extension mentioned above, the construction of the OCCS 100 using the existing parts but not using special (new) parts, if possible, also constitutes an important point in view of economy, development procedure, cost reduction and others.
However, in the case of the above-described conventional OCCS 100, the increase in the number of wavelengths being accommodated per optical fiber (namely, per input port) requires a substantial alteration of the configuration of the optical routing section 200, which is remote from excellent extensibility and economy. For example, in the configuration described above with reference to FIGS. 64 and 65, let it be assumed that, in the continuous satisfaction of the non-blocking conditions, the number n of wavelengths to be accommodated in each input port is increased from 32 to 128 and the total number N of input/output channels is increased from 256 to 1024.
In this case, in the optical routing section 200, as FIG. 66A shows, for the first-stage (third-stage) switch unit 200A (200C), 64 16=32 switch circuits 201 (32xc3x9716 switch circuits 203) each identical to that in the configuration shown in FIG. 65 can be put to use so that the increase in the numbers of the switch circuits 201 and 203 due to the extension is proportional to the increase in the number of wavelengths to be accommodated, whereas, for the second-stage switch unit 200B, there is a need to use 32 64xc3x9764 switch circuits 202xe2x80x2 different in basic switch size.
Thus, basically, the change of the basic switch size does not constitute the extension of the system. That is, as well known, of optical parts, a switch circuit for use in the optical routing section 200 especially encounters difficulty in large-scale integration and further creates serious problems in technique and cost, and an extremely disadvantageous situation exists in that there is a need to newly develop the 64xc3x9764 switch circuit 202xe2x80x2.
For the possible solution to this, conceivably, according to the principle configuration described above with reference to FIG. 64, as shown in FIG. 66B, each of the 64xc3x9764 switch circuits 202xe2x80x2 is reconstructed as a three-stage configuration comprising 8 16xc3x9716 switch circuits 202, 16 4xc3x978 switch circuits 202a and 16 8xc3x974 switch circuits 202b, which are implemented in basic switch sizes. However, in this instance, the optical routing section 200 results in a five-stage configuration as a whole, which causes the alteration of the system itself and is naturally remote from excellent extensibility.
In addition, in the case of increasing the number of wavelengths to be accommodated per input, since the interval (distance) between the wavelengths close to each other becomes extremely short, the band characteristics (an effective wavelength band, a transmission band characteristic, a wavelength splitting characteristic, and other characteristics) an optical device to be used requires become extremely severe, so limitation is imposed on optical devices available.
Incidentally, although a configuration to provide the extensibility to an OCCS in preparation for the increase in the number of optical fibers to be accommodated has been disclosed, for example, in Japanese Unexamined Patent Publication No. (Hei) 6-153248 or (Hei) 9-238370, these are merely for coping with the increase in the number of optical fibers, rather than for handling the xe2x80x9cextensibilityxe2x80x9d of the OCCS accompanying the increase in the number of wavelengths to be multiplexed per optical fiber at all. Accordingly, if the number of wavelengths to be multiplexed per optical fiber is increased under the techniques disclosed in the foregoing publications, the above-mentioned alteration in basic switch sizes and others will likewise take place.
As stated above, in an optical network using the WDM transmission technique, the number of wavelengths to be multiplexed is increased to deal with the increase in communication capacity, and the increase in the number of optical fibers, by contrast, is seldom taken for coping therewith. This is because the installation of new optical fibers incurs extremely high cost and the original purpose of the WDM transmission technique is to increase the volume of information to be communicated by utilizing the already installed optical fiber resource effectively. In addition, with an increase in the number of wavelengths to be accommodated per port, there is a need to relieve band characteristics, such as an effective wavelength band, a transmission band characteristic, a wavelength splitting characteristic and others, an optical device requires.
Accordingly, the present invention has been developed in consideration of the above-described objects, and it is therefore an object of the invention to less expensively provide an optical cross connect apparatus having excellent flexibility (extensibility) to cope with a change (particularly, an increase) in the number of wavelengths to be accommodated per input port, and additionally to provide an optical network equipped with the same optical cross connect.
For this purpose, according to an aspect of this invention, an optical cross connect apparatus comprises the following components:
(1) a plurality of input ports capable of accommodating optical signals of a plurality of kinds of input wavelengths, respectively;
(2) a plurality of output ports capable of accommodating optical signals of a plurality of kinds of output wavelengths;
(3) an optical input switch section using switch circuits corresponding in number to kinds of accommodation wavelengths for accommodating optical signals from the input ports for same input wavelength group to route the accommodated optical signals;
(4) an optical output switch section using switch circuits corresponding in number to the kinds of accommodation wavelengths for routing input optical signals to a desired output port for same output wavelength group;
(5) an optical multiplexing/distributing section provided between the optical input switch section and the optical output switch section, for multiplexing optical signals of the wavelengths after the routing operation by the switch circuits of the optical input switch section and for distributively outputting the resultant multiplexed optical signal as an input optical signal to the switch circuits of the optical output switch section; and
(6) an optical wavelength selecting section for conducting wavelength selecting processing to lead, of the multiplexed optical signal, an optical signal with a desired wavelength to a desired output port.
Thus, with the optical cross connect apparatus according to this invention, even if the number of accommodation wavelengths increases or decreases, a change in the number of switch circuits corresponding to this increase/decrease in only the input switch section and the output switch section can cope with the increase/decrease without changing the basic configuration of the optical multiplexing/distributing section, thereby economically realizing an optical cross connect apparatus showing extremely excellent flexibility on the increase/decrease in the number of wavelengths being accommodated.
In this case, in the aforesaid optical output switch section, it is also appropriate to provide a first wavelength converting section for converting an optical signal with an optional input wavelength after the routing operation by the switch circuits of the optical output switch section into an optical signal with a desired output wavelength so that the optical signal with the optional input wavelength coming in the optional input port is outputted as the optical signal with the desired output wavelength through the output port.
In addition, in the aforesaid optical input switch section, a second wavelength converting section, which converts an optical signal with an optical input wavelength before the routing operation by the switch circuits of the optical input switch section into an optical signal with a desired output wavelength can also be provided so that the optical signal with the optional input wavelength coming in the optional input port is outputted as the optical signal with the desired output wavelength through the output port.
Thus, the wavelength converting section, which converts an optical signal with an optional input wavelength into an optical signal with a desired output wavelength, is provided in the input switch section or in the output switch section so that the optical signal with the optional input wavelength to an optional input port is outputted as the optical signal with the desired output wavelength through a desired output port; therefore, it becomes possible to avoid the event that optical signals having the same wavelength are outputted simultaneously to the same output port to cause the optical signals with the same wavelength to interfere with each other, which contributes greatly to the improvement of reliability of this system.
Furthermore, if this optical cross connect apparatus accommodates k (k: an integer equal to or more than 2) input ports and k output ports, it is also appropriate that this optical cross connect apparatus is equipped with the following devices.
(1) Optical Input Switch Section
1) kxc3x972k switch circuits provided for same input wavelength group, each for accommodating k optical signals with the same input wavelength to route them to any one of 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) 2k first multiplexing/distributing units for multiplexing the outputs of the kxc3x972k switch circuits for different input wavelengths to distributively output the resultant multiplexed optical signal to routes corresponding in number to the kinds of accommodation wavelengths.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for same output wavelength group for accommodating outputs of the first multiplexing/distributing units for the same output wavelength to route the accommodated outputs to any one of the k outputs.
2) wavelength selectors provided for each of accommodation wavelengths for selecting, of the multiplexed optical signal after the routing operation by the 2kxc3x97k switch circuits, an optical signal having an input wavelength to be converted into a desired output wavelength.
3) wavelength converters provided for each accommodation wavelength for converting the wavelength of the optical signal selected by each of the wavelength selectors into the output wavelength.
In this case, the wavelength selectors constitute the optical wavelength selecting section, while the wavelength converters organize the first wavelength converting section.
Still furthermore, if k (k is an integer equal to or more than 2) input ports and k output ports are each provided to accommodate an optical signal having a plurality of kinds of wavelength bands each composed of a plurality of kinds of wavelengths, this optical cross connect apparatus can also be equipped with the following devices.
(1) Optical Input Switch Section
1) kxc3x972k switch circuits provided for same input wavelength group of each input wavelength bands, each for accommodating k optical signals with the same input wavelength in the same input wavelength band, coming in the input ports, and for routing them to any one of 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) 2k second multiplexing/distributing units for multiplexing outputs of the kxc3x972k switch circuits for different input wavelengths in the same input wavelength band, and for band-multiplexing the resultant multiplexed optical signals in the wavelength band to distributively output the band-multiplexed optical signal to routes corresponding in number to the kinds of accommodation wavelengths.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for output wavelength group of each output wavelength bands, each for accommodating 2k outputs of the second multiplexing/distributing units for the same output wavelength in the same output wavelength band to said output port and for routing the accommodated 2k outputs to any one of the k outputs.
2) wavelength selectors provided for each accommodation wavelength, each for selecting an optical signal with an input wavelength to be converted into a desired output wavelength from the multiplexed optical signal after the routing operation by the 2kxc3x97k switch circuits.
3) wavelength converters provided for each accommodation wavelength, each for converting the wavelength of the optical signal selected by the wavelength selector into an output wavelength.
Also, in this case, the aforesaid wavelength selectors constitute the optical wavelength selecting section, while the aforesaid wavelength converters organize the first wavelength converting section.
Moreover, if k (k is an integer equal to or more than 2) input ports and k output ports exist, this optical cross connect apparatus can also include the following devices.
(1) Optical Input Switch Section
1) wavelength converters provided for each accommodation wavelength, each for converting an optical signal with a wavelength from each of the input ports into a desired output wavelength.
2) kxc3x972k switch circuits provided for the input wavelength group, each for accommodating k outputs of the wavelength converters for the same input wavelength before the wavelength conversion and for routing the accommodated k outputs to any one of the 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) 2k first coupling/demultiplexing units for coupling the outputs of the kxc3x972k switch circuits for different input wavelengths before the wavelength conversion and further for demultiplexing the coupled signal.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for the output wavelength group, each for accommodating the 2k outputs of the first coupling/demultiplexing units for the same output wavelength to the output ports and for routing the accommodated 2k outputs to any one of the k outputs.
In this case, the aforesaid first coupling/demultiplexing units constitute the optical wavelength selecting section, while the aforesaid wavelength converters organize the second wavelength converting section.
Furthermore, if k (k is an integer equal to or more than 2) input ports and k output ports are provided to each accommodates an optical signal having a plurality of kinds of wavelength bands each composed of a plurality of kinds of wavelengths, this optical cross connect apparatus can also be equipped with the following devices.
(1) Optical Input Switch Section
1) wavelength converters provided for each accommodation wavelength, and each of which is capable of converting an optical signal having the wavelength from each of the input ports into a desired output wavelength.
2) kxc3x972k switch circuits provided for the input wavelength group of each input wavelength bands, each for accommodating k optical signals with the same input wavelength in the same input wavelength band, coming in the input ports, and for routing them to any one of the 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) second coupling/demultiplexing units each for coupling the outputs of the kxc3x972k switch circuits for different input wavelengths before the wavelength conversion and then for band-demultiplexing the coupled output signal into optical signals pertaining to the wavelength bands to demultiplex an optical signal pertaining to each of the wavelength bands after the band demultiplexing.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for the output wavelength group of each output wavelength bands, each for accommodating the outputs of the aforesaid second coupling/demultiplexing units for the same output wavelength in the same output wavelength band to the output ports and for routing them to any one of the k outputs.
In this case, the aforesaid second coupling/demultiplexing units constitute the optical wavelength selecting section, while the aforesaid wavelength converters organize the second wavelength converting section.
Still furthermore, if k (k is an integer equal to or more than 2) input ports and k output ports exist, this optical cross connect apparatus can also include the following devices.
(1) Optical Input Switch Section
1) kxc3x972k switch circuits provided for the input wavelength group, each for accommodating k optical signals with the same input wavelength, coming in the input ports, and for routing them to any one of 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) 2k first coupling/distributing units each for coupling the outputs of the kxc3x972k switch circuits for different input wavelengths and for distributively outputting the resultant coupled optical signal to routes corresponding in number to the kinds of accommodation wavelengths.
2) wavelength selectors provided for each of the distributed output signals, each for selecting an optical signal having an input wavelength to be converted into a desired output wavelength, from each of the distributed output signals of the first coupling/distributing units.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for the output wavelength group, each for accommodating the 2k outputs of the wavelength selectors for the same output wavelength and for routing the accommodated 2k outputs to any one of k outputs.
2) wavelength converters provided for all the accommodation wavelengths, each for converting the output of the 2kxc3x97k switch circuit into the desired output wavelength.
In this case, the aforesaid wavelength selectors constitute the optical wavelength selecting section, while the aforesaid wavelength converters organize the first wavelength converting section.
Yet furthermore, if k (k is an integer equal to or more than 2) input ports and k output ports are provided to each accommodates an optical signal having a plurality of kinds of wavelength bands each composed of a plurality of kinds of wavelengths, this optical cross connect apparatus can also be equipped with the following devices.
(1) Optical Input Switch Section
1) kxc3x972k switch circuits provided for the input wavelength group of each input wavelength bands, each for accommodating k optical signals with the same input wavelength in the same input wavelength band, coming in the input ports and for routing them to any one of the 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) 2k second coupling/distributing units each for coupling the outputs of the kxc3x972k switch circuits for different input wavelengths and for distributively outputting the resultant coupled output signal to routes corresponding in number to all the kinds of accommodation wavelengths.
2) wavelength selectors provided for each of distributed output signals, each for selecting, from the distributed output signals of the second coupling/distributing units, an optical signal having an input wavelength to be converted into a desired output wavelength.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for same output wavelength group of each output wavelength bands, each for accommodating the 2k outputs of the wavelength selectors for the same output wavelength in the same output wavelength band to the output ports and for routing the accommodated 2k outputs to any one of the k outputs.
2) wavelength converters provided for each accommodation wavelength, each for converting the wavelength of each of the optical signals from the 2kxc3x97k switch circuits into the output wavelength.
In this case, the wavelength selectors constitute the optical wavelength selecting section, while the wavelength converters constitute the first wavelength converting section.
Moreover, k input ports (k is equal to or more than 2) and k output ports are provided, this optical cross connect apparatus can include the following devices.
(1) Optical Input Switch Section
1) wavelength converters provided for each accommodation wavelength, each for converting an optical signal having each of the wavelengths from the input ports into a desired output wavelength.
2) kxc3x972k switch circuits provided for same input wavelength group, each for accommodating the k outputs of the wavelength converters for the same input wavelength before the wavelength conversion and for routing the accommodated k outputs to any one of the 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) 2k third coupling/distributing units for coupling the outputs of the kxc3x972k switch circuits for different input wavelengths before the wavelength conversion and for distributively outputting the resultant coupled output signal to routes corresponding in number to the kinds of accommodation wavelengths.
2) wavelength selectors provided for each distributed output signal, each for selecting, from the distributed output signals of the third coupling/distributing units, an optical signal having an input wavelength to be converted into a desired output wavelength.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for the output wavelength group, each for accommodating the 2k outputs of the wavelength selectors for the same output wavelength to the output ports and for routing the accommodated 2k outputs to any one of the k outputs.
In this case, the wavelength selectors constitute the optical wavelength selecting section, while the wavelength converters constitute the second wavelength converting section.
Furthermore, if k (k is an integer equal to or more than 2) input ports and k output ports are provided to each accommodates an optical signal having a plurality of kinds of wavelength bands each composed of a plurality of kinds of wavelengths, this optical cross connect apparatus can also be equipped with the following devices.
(1) Optical Input Switch Section
1) wavelength converters provided for each accommodation wavelength, each capable of converting an optical signal with an wavelength from each of the input ports into a desired output wavelength.
2) kxc3x972k switch circuits provided for the input wavelength group of each input wavelength bands, each for accommodating k optical signals having the same input wavelength in the same input wavelength band, coming in the input ports, and for routing the accommodated k optical signals to any one of the 2k outputs.
(2) Optical Multiplexing/Distributing Section
1) 2k fourth coupling/distributing units each for combining the outputs of the kxc3x972k switch circuits for different input wavelengths before the wavelength conversion and for distributively outputting the resultant coupled output signal to routes corresponding in number to the kinds of accommodation wavelengths.
2) wavelength selectors provided for each distributed output signal, each for selecting, from the distributed output signals of the fourth coupling/distributing units, an optical signal having an input wavelength to be converted into-a desired output wavelength.
(3) Optical Output Switch Section
1) 2kxc3x97k switch circuits provided for the output wavelength group of each output wavelength bands, each for accommodating the 2k outputs of the wavelength selectors for the same output wavelength in the same output wavelength band to the output ports and for routing the accommodated 2k outputs to any one of the k outputs.
In this case, the wavelength selectors constitute the optical wavelength selecting section, while the wavelength converters organize the second wavelength converting section.
As described above, in a case in which the input ports (output ports) are k in number, the input switch section and the output switch section can accept the use of the existing (kxc3x972k) switch circuit and the existing (2kxc3x97k) switch circuit, while the optical multiplexing/distributing section can accept the employment of the optical parts, such as a multiplexing/distributing unit, a coupling/demultiplexing unit, which have been used in the existing WDM transmission system; therefore, there is no need to newly design and develop optical parts even if an increase/decrease in the number of wavelengths to be accommodated takes place, thus realizing a system according to this invention within an extremely short period of time and at an extremely low cost.
In addition, even in a case in which optical signals pertaining to a plurality of types of wavelength bands, each of which is composed of optical signals of a plurality of kinds of wavelengths, are accommodated per port, if the (kxc3x972k) switch circuit and (2kxc3x97k) switch circuit are used for the input switch section and the output switch section for each of the above-mentioned wavelengths while a multiplexing/distributing unit or the like capable of accomplishing the multiplexing/distribution at each wavelength is additionally incorporated into the optical multiplexing/distributing section (some configurations do not require the additional installation thereof), it is possible to cope with this case, thus realizing a larger-capacity optical cross connect apparatus within a short period of time and at a low cost.
Still additionally, in this optical cross connect apparatus, it is also appropriate that each of the above-mentioned input ports each accommodates a wavelength-multiplexed optical signal having a plurality of kinds of input wavelengths while each of the above-mentioned output ports accommodates a wavelength-multiplexed optical signal having a plurality of kinds of output wavelengths.
Moreover, in this optical cross connect apparatus, it is also appropriate that a portion of the above-mentioned input ports each accommodates a wavelength-multiplexed optical signal having a plurality of kinds of input wavelengths while the remaining input ports are each used for adding an optical signal having an arbitrary wavelength, and a portion of the above-mentioned output ports each accommodates a wavelength-multiplexed optical signal having a plurality of kinds of output wavelengths while the remaining output ports are each used for dropping an optical signal having an arbitrary wavelength.
Furthermore, in this optical cross connect apparatus, it is also possible that only the output ports each accommodates a wavelength-multiplexed optical signal having a plurality of kinds of output wavelengths, or that only the input ports each accommodates a wavelength-multiplexed optical signal having a plurality of kinds of wavelengths.
Thus, if a portion of or all of each of the input ports and the output ports, or either the input ports or the output ports is made to accommodate a wavelength-multiplexed optical signal having a plurality of kinds of wavelengths, each of the ports can be allocated properly to dedicated station-to-station transmission, station-to-station/in-station transmission, transmission terminal stations, receive terminal station and others, thereby realizing and providing an optical cross connect apparatus suitable for desired using modes with considerable ease.
In addition, in accordance with this invention, there is provided an optical network including at least one optical cross connect apparatus having the above-described configuration.
Accordingly, when an optical network is constructed using each of the above-described optical cross connect apparatus, an optical network capable of setting various alternative routes at the occurrence of troubles becomes realizable.
In addition, the optical cross connect apparatus according to this invention is characterized by comprising the following sections:
(1) a plurality of input ports for accommodating optical signals of a plurality of kinds of input wavelengths;
(2) a plurality of output ports for accommodating optical signals of a plurality of kinds of output wavelengths;
(3) an input wavelength converting section for converting the input wavelengths into intra-apparatus wavelengths less in number of kinds than the number of kinds of input wavelengths;
(4) a wavelength multiplexing/distribution routing section for multiplexing, in terms of wavelengths, optical signals with the intra-apparatus wavelengths from the aforesaid input wavelength converting section to distribute and route the resultant intra-apparatus wavelength multiplexed optical signal as an optical signal including a desired output wavelength to a desired output port;
(5) an optical wavelength selecting section for selecting an optical signal with a desired intra-apparatus wavelength from the wavelength multiplexed optical signal; and
(6) an output wavelength converting section for converting the wavelength of the optical signal, selected by the optical wavelength selecting section, into the aforesaid output wavelength.
In this case, when the numbers of the input ports and the output ports are respectively taken as k (k is an integer equal to or more than 2), the number of kinds of wavelengths each of the ports accommodates is taken as n (n is an integer equal to or more than 2) and the number of kinds of intra-apparatus wavelengths is taken as m (m is an integer which satisfies 2xe2x89xa6m less than n), the input wavelength converting section, preferably the wavelength multiplexing/distribution routing section and the output wavelength converting section are constructed, for example, as follows.
1) Input Wavelength Converting Section
m fixed wavelength converting sections for converting the optical signals of the aforesaid input wavelengths into optical signals of the same intra-apparatus wavelengths in units of p waves [where p is an integer satisfying p=n/m ( less than k)].
2) Wavelength Multiplexing/Distribution Routing Section
a) n kxc3x972k switches each for accommodating the k outputs of the fixed wavelength converting sections for same input wavelength before the wavelength conversion into the intra-apparatus wavelengths to route the accommodated k outputs to any one of 2k outputs.
b) 2k nxc3x97n routing sections for multiplexing, in terms of wavelengths, optical signals with p sets of different intra-apparatus wavelengths from the kxc3x972k switches to distributively route the resultant intra-apparatus wavelength multiplexed optical signal.
c) n 2kxc3x97k switches each for accommodating the outputs of the nxc3x97n routing sections at every intra-apparatus wavelength to be converted into the same output wavelength to route them to a desired output port.
3) Output Wavelength Converting Section L
kxc3x97n fixed output wavelength converters for converting the outputs of the 2kxc3x97k switches into optical signals of predetermined output wavelengths.
In addition, it is also appropriate that each of the nxc3x97n routing sections includes p m:n multiplexing/distributing sections for multiplexing, in terms of wavelengths, optical signals of p sets of different intra-apparatus wavelengths from the kxc3x972k switches and further for distributing the resultant intra-apparatus wavelength multiplexed optical signal in the form of n optical signals, n pxc3x971 switches each for selecting a desired intra-apparatus wavelength multiplexed optical signal from the p sets of intra-apparatus wavelength multiplexed optical signals from the m:n multiplexing/distributing sections, and n tunable (variable) wavelength filters each for selecting an optical signal of desired intra-apparatus wavelengths from the outputs of the pxc3x971 switches, with n tunable wavelength filters constituting the aforesaid optical wavelength selecting section.
Still additionally, it is also appropriate that each of the nxc3x97n routing sections includes m pxc3x972p switches each for accommodating optical signals of p sets of different intra-apparatus wavelengths from the kxc3x972k switches for same intra-apparatus wavelength to route them to arbitrary routes, 2p m:m multiplexing/distributing sections for multiplexing the different intra-apparatus wavelengths of the outputs of the pxc3x972p switches to distribute the resultant intra-apparatus wavelength multiplexed optical signal in the form of m optical signals, m 2pxc3x97p switches each for routing the 2p outputs from the m:m multiplexing/distributing sections to any one of p outputs, and n tunable wavelength filters each for selecting an optical signal of desired intra-apparatus wavelength from the outputs of the 2pxc3x97p switches, with the n tunable wavelength filters constituting the aforesaid optical wavelength selecting section.
Furthermore, it is also appropriate that the aforesaid optical wavelength selecting section includes n tunable wavelength filters provided outside the nxc3x97n routing section but not provided inside the nxc3x97n routing section, for example, provided at a rear stage of each of the aforesaid 2kxc3x97k switches for selecting an optical signal with a desired intra-apparatus wavelength from the intra-apparatus wavelength multiplexed optical signal from the 2kxc3x97k switches.
In this case, preferably each of the nxc3x97n routing sections includes p m:n multiplexing/distributing sections for multiplexing, in terms of wavelengths, optical signals of p sets of different intra-apparatus wavelengths from the kxc3x972k switches to distribute the resultant intra-apparatus wavelength multiplexed optical signal in the form of n optical signals, and n pxc3x971 switches each for selecting a desired intra-apparatus wavelength multiplexed signal from the outputs of the m:n multiplexing/distributing sections.
Additionally, in this case, it is also possible that each of the nxc3x97n routing sections includes m pxc3x972p switches each for accommodating optical signals of p sets of different intra-apparatus wavelengths from the kxc3x972k switches to route them to any one of 2p outputs, 2p m:m multiplexing/distributing sections for multiplexing different intra-apparatus wavelengths of the outputs of the pxc3x972p switches to distribute the resultant wavelength multiplexed optical signal in the form of m optical signals, and m 2pxc3x97p switches for routing the 2p outputs from the m:m multiplexing/distributing sections to any one of p outputs.
In this instance, it is also possible that each of the m:m multiplexing/distributing sections is constructed as an m:m routing section including M (M less than m) (m/M)xc3x97(2m/M) switches each for accommodating, of the outputs of the pxc3x972p switches, optical signals with the same intra-apparatus wavelength to route them to arbitrary routes, 2m/M M:M couplers for multiplexing different intra-apparatus wavelengths of optical signals from the (m/M)xc3x97(2m/M) switches to distribute the resultant wavelength multiplexed optical signal in the form of M optical signals, and M (2m/M)xc3x97(m/M) switches for routing the outputs from the M:M couplers to any one of (m/M) outputs. Meanwhile, the input wavelength converting section, the wavelength multiplexing/distribution routing section and the output wavelength converting section can be constructed in a state equipped with the following sections
1) Input Wavelength Converting Section
kxc3x97n variable wavelength converters for converting optical signals of input wavelengths into optical signals of arbitrary intra-apparatus wavelengths of p sets of different intra-apparatus wavelengths.
2) Wavelength Multiplexing/Distribution Routing Section
a) an optical input switch section having n kxc3x972k switches each for accommodating optical signals from the variable wavelength converters for same input wavelength prior to intra-apparatus wavelength conversion to route them;
b) 2k nxc3x97n routing sections for multiplexing, in terms of wavelengths, optical signals of p sets of different intra-apparatus wavelengths from the kxc3x972k switches to distributively route the resultant intra-apparatus wavelength multiplexed optical signal; and
c) an optical output switch section having n 2kxc3x97k switches each for accommodating the outputs from the nxc3x97n routing sections at every intra-apparatus wavelength to be converted into the same output wavelength to route them to desired output ports.
3) Output Wavelength Converting Section
kxc3x97n fixed output wavelength converters for converting optical signals of p sets of identical intra-apparatus wavelengths from the 2kxc3x97k switches into optical signals of predetermined output wavelengths.
In this case, preferably each of the nxc3x97n routing sections includes p m:n multiplexing/distributing sections for multiplexing, in terms of wavelengths, optical signals of p sets of different intra-apparatus wavelengths from the kxc3x972k switches to distribute the resultant intra-apparatus wavelength multiplexed optical signal in the form of n optical signals, n pxc3x971 switches for selecting desired intra-apparatus wavelength multiplexed optical signals from the p sets of intra-apparatus wavelength multiplexed optical signals of the m:n multiplexing/distributing sections, and n fixed wavelength filters for selecting optical signals of predetermined intra-apparatus wavelengths from the outputs of pxc3x971 switches, with the n fixed wavelength filters constituting the aforesaid optical wavelength selecting section.
Furthermore, it is also appropriate that each of the nxc3x97n routing sections includes m pxc3x972p switches each for routing the optical signals of the p sets of different intra-apparatus wavelengths from the kxc3x972k switches to any one of 2p outputs, 2p m:m multiplexing/distributing sections for multiplexing the outputs of the pxc3x972p switches for different intra-apparatus wavelengths to distribute the resultant intra-apparatus wavelength multiplexed optical signal in the form of m optical signals, m 2pxc3x97p switches each for routing the 2p sets of outputs from m:m multiplexing/distributing sections to desired 2kxc3x97k switches, and n fixed wavelength filters each for selecting an optical signal of predetermined intra-apparatus wavelength from the outputs of the 2pxc3x97p switches, with the n fixed wavelength filters constituting the aforesaid optical wavelength selecting section.
Also in this case, the aforesaid optical wavelength selecting section can be provided in the exterior of the nxc3x97n routing section but not in the interior thereof. That is, it is also possible to use n fixed wavelength filters for selecting an optical signal of predetermined intra-apparatus wavelengths from the outputs of the 2kxc3x97k switches.
In this instance, preferably each of the nxc3x97n routing sections includes m pxc3x972p switches each for routing optical signals of p sets of different intra-apparatus wavelengths from the aforesaid kxc3x972k switches to any one of 2p outputs, 2p m:m multiplexing/distributing sections for multiplexing different intra-apparatus wavelengths of the outputs of the pxc3x972p switches to distribute the resultant intra-apparatus wavelength multiplexed optical signal in the form of m optical signals, and m 2pxc3x97p switches each for routing the 2p sets of outputs of the m:m multiplexing/distributing sections to desired 2kxc3x97k switches.
In this case, it is also appropriate that each of the m:m multiplexing/distributing sections is constructed as an m:m routing section including M (M less than m) (m/M)xc3x97(2m/M) switches for accommodating (m/M)optical signals of arbitrary intra-apparatus wavelengths from the aforesaid pxc3x972p switches to route them to any one of (2m/M) outputs, 2m/M M:M couplers for multiplexing, in terms of wavelengths, optical signals of different intra-apparatus wavelengths from the (m/M)xc3x97(2m/M) switches to distribute the resultant intra-apparatus wavelength multiplexed optical signal in the form of M optical signals, and M (2m/M)xc3x97(m/M) switches each for routing the 2m/M outputs from the M:M couplers to desired 2kxc3x97k switches.
As the above-mentioned intra-apparatus wavelengths, continuous wavelength-grid wavelengths are acceptable, and incontinuous wavelength-grid wavelengths are also acceptable. Furthermore, it is also possible that the above-mentioned multiplexing/distribution routing section is replaceable with the existing routing section which does not perform the wavelength multiplexing/distribution. That is, an optical cross connect apparatus according to this invention can be composed of the following parts:
(1) a plurality of input ports for accepting optical signals of a plurality of kinds of input wavelengths;
(2) a plurality of output ports for accepting optical signals of a plurality of kinds of output wavelengths;
(3) an input wavelength converting section for converting optical signals of a plurality of kinds of input wavelengths inputted from the input ports into intra-apparatus wavelengths less in number of kinds than the input wavelengths;
(4) a routing section for routing optical signals of intra-apparatus wavelengths from the input wavelength converting section to desired output ports; and
(5) an output wavelength converting section for converting the wavelengths of the optical signals from the routing section into predetermined output wavelengths.
As described above, according to the optical cross connect apparatus, in a state where input wavelengths are converted into intra-apparatus wavelengths to decrease the number of wavelengths to be handled in the interior of the apparatus while optical signals of the intra-apparatus wavelengths are multiplexed in terms of these wavelengths, the optical signals are distributively routed and optical signals of intra-apparatus wavelengths to be converted into desired output wavelengths to desired output ports are selected from the intra-apparatus wavelength multiplexed optical signals. Accordingly, the given band characteristics required in optical devices to be put to use can be relieved so that, with respect to an increase/decrease (particularly, increase) in number of input wavelengths per port, it is possible to use the existing optical devices, the existing optical switch techniques and the existing wavelength multiplexing techniques. This can provide economically a large-capacity optical cross connect apparatus exhibiting an excellent flexibility (extensibility) with respect to the increase/decrease in number of input wavelengths per port, without requiring new technical developments.
In this case, the wavelength conversion of the input wavelengths into the intra-apparatus wavelengths can be done by converting the input wavelengths into predetermined wavelengths through the use of fixed input wavelength converters, alternatively can rely on the conversion thereof into wavelengths corresponding to arbitrary output wavelengths through the use of variable input wavelength converters. In either case, the aforesaid wavelength selection processing can be conducted at a front stage of the optical output switch section (2kxc3x97k switches) or at a rear stage thereof, which can increase the choices of apparatus configuration.
Particularly, in the case in which the aforesaid wavelength selection processing is conducted at a rear stage of the optical output switch section (2kxc3x97k switches), it is possible to cut the number of variable/fixed wavelength filters required so that the apparatus scale is reducible. Additionally, in this case, when the m:m multiplexing/distributing sections for wavelength-multiplexing and distributing the optical signals of the intra-apparatus wavelengths are constructed as wavelength multiplexing/distribution m:m routing sections, a further decrease in number of intra-apparatus wavelengths is feasible, which can additionally relieve the given band characteristics required in optical devices to be put to use.
If continuous wavelength-grid wavelengths are allocated to the aforesaid intra-apparatus wavelengths, it is possible to relieve the effective wavelength band to be required in optical devices to be put to use. On the other hand, if incontinuous wavelength-grid wavelengths are allocated thereto, it is possible to ease the transmission band characteristics the optical wavelength selecting section is required to have. In both cases, a large-capacity optical cross connect apparatus is realizable easily using the existing optical devices.
Incidentally, the optical signal routing after the conversion into the intra-apparatus wavelengths is also achievable using the existing routing processing which does not perform the wavelength multiplexing/distribution, also in which case, it is possible to ease the band characteristics required in optical devices to be put to use.